1. Field of the Invention
The present invention relates to nanocoupling of a polymer onto a surface of a metal substrate for improving coating adhesion of the polymer onto the surface of the metal substrate, and in vivo stability and durability of the polymer.
2. Background of the Invention
Recently, aging of a population gives rise to rapid increase in use of metal implants or the like. The metal implants have been used as materials for stents in vascular and nonvascular systems, mechanical valves, and an articular, a spinal, a dental and an orthopedic implants, and the like. However, the metal implant may cause an accurate closure due to thrombosis after surgical operation. The metal implant may also act as a traumatic element onto endothelium to result in an neointima proliferation, which may cause restenosis, inflammatory response and the like, and even cause tissue necrosis in serious cases.
Surface modification for rendering biocompatibility to the metal implants enhances biocompatibility while maintaining superior mechanical properties of the metal. A representative of the metal surface modification method is a chemical surface treatment. However, the chemical surface treatment may cause the metal surface to be rough, and also may decrease biocompatibility due to use of a toxic material in vivo.
Another surface modification method is to coat a biodegradable polymer onto a surface of a metal implant. Here, a typically used biodegradable polymer may include polyglycolic acid (PGA), poly-L-lactic acid (PLLA), poly-D,L-lactic acid (PDLLA), polylactic-co-glycolic acid (PLGA), poly-ε-carprolactone (PCL), polyaminoic acid, polyanhydride (PA), polyorthoester (POE), or copolymers thereof. However, in case of coating the biodegradable polymer through an air spray or ultrasonic coating, the coated polymer is separated from the surface of the metal implant within a short time, and accordingly, the metal implant is exposed to blood and tissue cells, which may cause several problems, such as restenosis, blood coagulation, drug release within a short period of time, high cytotoxicity, decrease of cell adhesion, inflammatory response inevitably accompanied with infiltration of bacteria and the like. Therefore, improvement of the coating adhesion of the biodegradable polymers coated on the metal implant is recognized as a very important factor for improving the function of the metal implant.